Two different types of 2-thienyl bridge in dinuclear manganese and rhenium compounds

Abstract

Thermal and photochemical reactions of diphenyl-2-thienylphosphine (L) with [Mn₂(CO)₁₀] gave simple substitution products [Mn₂(CO)_10 – nL_n] 1 (n = 1) and 2 (n = 2) with ligand L co-ordinated through the phosphorus atom. Under forcing conditions (refluxing xylene) oxidative addition with P–C cleavage occurred to give the µ-2-thienyl complex [Mn₂(CO)₆(µ-PPh₂)(µ-η¹∶η⁵-C₄H₃S)] 3. Loss of CO and P–C bond cleavage do not occur so easily in the case of [Re₂(CO)₁₀]. UV Treatment of the rhenium carbonyl with L gave [Re₂(CO)₈(µ-P,S-Ph₂PC₄H₃S)] 4, in which the ligand L is bridging through the two heteroatoms. Oxidative addition occurs internally at about 180° in decane with rupture of a P–C bond to produce an isomer of 4, [Re₂(CO)₈(µ-PPh₂)(µ-η¹∶η¹-C,S-C₄H₃S)] 5. Crystal structures revealed a novel form of bridging of L co-ordinated through P and S in 4 and two different modes of 2-thienyl bridge (µ-η²∶η⁵ and µ-η¹∶η¹-C,S) in 3 and 5 respectively. With the previously known µ-η¹∶η²-bridging form of thienyl, these new compounds 3 and 5 provide three distinct type of thienyl bridge. The type of bridge which is formed depends upon the electronic requirements of the metal atoms and the span between them.